After exploring and doing all the side quests you wanted in Pleasant River, head to King St and go north towards the drawbridge. Enter the control tower to the left of the bridge, climb the ladder, and pull the red lever on the wall. The bridge will lower, allowing you to pass to the Port district.
Cross the bridge. When you reach a junction with a big truck in it, turn left and enter the house to the left. Explore this house. See map for the quest start exact location, X marks the spot:
In one of the rooms near the entrance, there is a mirror with a murky view. Murphy says, "Wait, what's wrong with this picture?" to give you a hint that there is a sidequest to do here.
This is a side quest, Mirror Mirror. Your objective is to Make the reflection tell the truth.
Mirror, Mirror Puzzle Solution
This puzzle is a fun one, similar to "spot the difference" puzzles you might have done as a kid, where you had to look at two pictures and find all the differences. Approach the mirror to get a more focused picture of the room. The mirror will show you a reflection of the room, but something is different. You then have to interact with an object in the room to make it the same as in the mirror. You will be repeating this process five times.
Tip#1: After doing each of the steps below, go back to the mirror. Don't do them all at once
Tip#2: Each time you go to the mirror, the room resets. That is ok. Keep following the steps
Tip#3: If you do not manipulate the objects in the room in the order listed in this guide, or you just touch them randomly, you will get an invisible Screamer encounter. This Screamer will attack you, but you can only see it in the mirror. Use the mirror to help you determine it's location, but do not attack the reflection of the Screamer in the mirror. Attack the actual location of the Screamer in the room, even if you cannot see it.
The Spot the Difference puzzle solution is as follows.
1) Lamp - The Lamp on the side table in the corner, near the couch, is turned ON in the mirror, but OFF in the room. Turn on the lamp.
2) Dresser drawer - In the mirror, the drawer is open. In the room itself, it is closed. Open the dresser drawer.
3) Television - In mirror picture, television is turned on. In real room picture, it is not. Turn on the TV.
4) Portrait - In the mirror, portrait is rotated. In the room, portrait is upside down. Rotate the Painting.
5) Candle - In portrait, candle is lit. In the room, candle is not lit. Use your lighter and Light the Candle.
The mirror shatters to reveal a secret room behind it. Enter the hidden room behind the mirror. There are two first aid kits and two pistol bullet boxes inside. There is also a Mystery Object on the ground. Pick up the mystery item to add it to your journal. It is a letter from Dr. Ari Richmond of Silent Hill Psychiatry & Family Counseling about a lady who does mundane repetitive tasks around the house because of her fear from the "people in the mirror".
You unlock the achievement/trophy:
Spot the Difference
Completed the "Mirror, Mirror" side quest.